1. Field of the Invention
This invention relates to a mower comprising a first chassis by which it is hitched to a tractor, a second chassis supporting the work elements and connected to the first chassis by connecting rods constituting a deformable quadrilateral, particularly in an upward directed direction to make it possible for the second chassis and for the work elements that it supports to adapt to the contours of the ground.
2. Background of the Related Art
Such a mower is described in FR-A-2,458,981. This known mower comprises a first chassis which is formed by a frame of approximately rectangular shape, placed vertically and perpendicular to the direction of work. To this frame is fastened a hitching device intended to be hitched to the front hitch of a tractor. At each of the lateral ends of the frame of this first chassis, gussets are provided to each of which are connected--by joints with axes that extend horizontally and perpendicular to the direction of work--two connecting rods that extend backward and downward. At its back end, each connecting rod is connected, by a joint with an axis that is also horizontal and perpendicular to the direction of work, to a second chassis supporting cutting elements in the form of rotary disks provided with blades. These connecting rods form a parallelogram deformable in an upward directed direction. The second chassis comprises a U-shaped frame which is open backward and extends in an approximately horizontal plane. At the back part of each leg of the U, the frame is connected to an arm that extends downward and is provided at its lower end with a lug directed frontward in the direction of work. At their front end, these lugs are connected to a housing that extends perpendicular to the direction of work and above which said disks turn which are guided there in rotation. The frame of the first chassis also supports a first housing driven by a first universal joint telescopic drive shaft connected to the power takeoff of the tractor. This first housing, by means of a universal joint telescopic shaft, drives a second housing fastened to the frame of the second chassis and intended to transmit the movement to the disks.
Thanks to the connecting rods which connect the second chassis to the first chassis and which form at least approximately a parallelogram deformable in an upward directed direction, the second chassis and the cutting elements that it supports, can indeed adapt to the configuration of the ground on which the mower must work. As these connecting rods constitute at least approximately a drawn parallelogram, the second chassis slides more easily over the ground.
Although the second chassis can theoretically easily pass over bumps and obstacles, it has been proved in practice that deformations, indeed breaks, can appear particularly at the places on the second chassis where the upper connecting rods of the deformable parallelogram are connected, when said second chassis and/or cutting elements hook a large obstacle. These problems of breaks and deformations result particularly from the fact that the connecting points of the connecting rods of the deformable parallelogram on the second chassis extend a relatively great distance from the ground. Thus, when the cutting elements and/or the lower part of the second chassis hook an obstacle, the generated force acts on a relatively great lever arm.
In EP-A-0,277,343 a mower is described which is intended to be hitched to the back of a tractor. This known mower comprises a first chassis which is equipped with two wheels by which it rests on the ground, and with a hitching beam by which the mower is hitched to the tractor. This known mower comprises, moreover, a second chassis which supports cutting elements made in the form of rotary drums equipped with blades. This second chassis is connected to the first chassis by two pairs of connecting rods forming a parallelogram deformable in an upward direction. These connecting rods are connected at their back end to the second chassis and at their front end to the first chassis. This known mower comprises also a first housing fastened to the second chassis in its middle part and a second housing also fastened to the second chassis at a place offset crosswise in relation to the first housing and receiving the movement provided by the first housing by means of belts rotating in a horizontal plane.
In this known mower, the connecting points of the connecting rods of the deformable parallelogram on the second chassis also extend a relatively great distance from the ground. Thus this known mower should be subject to the same problems as those mentioned above, since the force generated when the rotary drums hook an obstacle also acts a very great lever arm.
In DE-A-1,782,238 a mower is described which comprises a chassis by which the mower is hitched to a tractor. This known mower, moreover, comprises cutting elements made in the form of rotary drums equipped with blades on their lower periphery. Each cutting element is connected to the chassis by connecting rods forming a parallelogram deformable in an upward direction. At the top of each rotary drum a bevel drive gear is placed that is used to drive the drum in rotation. The lead wheel of each bevel drive gear is connected in rotation to a respective shaft whose axis of rotation extends horizontal and perpendicular to the direction of work. These various shafts are connected in rotation to one another by universal joint telescopic shafts. The axes of the joints by which the lower connecting rods are connected to their corresponding cutting element are merged with the axis of rotation of the respective shaft. The upper connecting rod is equipped with a release safety device which, in case the drum hooks an obstacle, allows the shortening of said upper connecting rod and permits the drum to pivot backward around the axes of the joints of the lower connecting rods. In this known mower, no housing is provided that is intended to provide to the cutting elements the movement received from the power takeoff of the tractor. Moreover, it has been proved in practice that it was not desirable to incorporate the safety device in the connecting rods of the parallelogram. In addition, it appears that the various cutting elements can have among them only a minimum relative clearance. This results from the fact that the universal joint shaft, provided between two cutting elements, necessarily has a relatively short length, so that the angles that the universal joints can take very quickly exceed the admissible limit angles.